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| United States Patent |
5,638,100
|
|
Kanematsu
, et al.
|
June 10, 1997
|
Ink jet and ink preliminary ejecting method
Abstract
An ink jet apparatus includes an ink jet head having a plurality of
ejecting ports arranged in a predetermined pattern and a plurality of heat
generating elements arranged corresponding to the ejecting ports, and a
driving controlling means for applying a driving signal to heat generating
elements 1e in response to a driving information wherein a printing mode
of printing a printing medium by ejecting ink from the ejecting ports and
a preliminary ejecting mode of performing no ejection toward the printing
medium are settled for the apparatus. The driving controlling means
includes a defoaming position changing means for changing the position of
a defoaming point P.sub.B arising on each heat generating element 1e when
ink is ejected in conformity with the preliminary ejecting mode. With this
construction, a density fluctuation in character, image or the like can be
eliminated, and moreover, a quantity of consumption of ink usable for
preliminary ejection can be reduced compared with a conventional ink jet
apparatus. In addition, an ink preliminary ejecting method to be practiced
by the ink jet apparatus is also provided.
| Inventors:
|
Kanematsu; Daigoro (Yokohama, JP);
Otsuka; Naoji (Yokohama, JP);
Yano; Kentaro (Yokohama, JP);
Iwasaki; Osamu (Kawasaki, JP)
|
| Assignee:
|
Canon Kabushiki Kaisha (Tokyo, JP)
|
| Appl. No.:
|
508249 |
| Filed:
|
July 27, 1995 |
Foreign Application Priority Data
| Current U.S. Class: |
347/35; 347/57 |
| Intern'l Class: |
B41J 002/05 |
| Field of Search: |
347/35,22,57,67,26
|
References Cited
U.S. Patent Documents
| 4313124 | Jan., 1982 | Hara.
| |
| 4345262 | Aug., 1982 | Shirato et al.
| |
| 4459600 | Jul., 1984 | Sato et al.
| |
| 4463359 | Jul., 1984 | Ayata et al.
| |
| 4558333 | Dec., 1985 | Sugitani et al.
| |
| 4608577 | Aug., 1986 | Hori.
| |
| 4723129 | Feb., 1988 | Endo et al.
| |
| 4740796 | Apr., 1988 | Endo et al.
| |
| 5166699 | Nov., 1992 | Yano et al.
| |
| 5367325 | Nov., 1994 | Yano et al.
| |
| 5440330 | Aug., 1995 | Anderson | 347/26.
|
| Foreign Patent Documents |
| 59-123670 | Jul., 1984 | JP | .
|
| 59-138461 | Aug., 1984 | JP | .
|
Primary Examiner: Hartary; Joseph W.
Attorney, Agent or Firm: Fitzpatrick, Cella, Harper & Scinto
Claims
What is claimed is:
1. An ink jet apparatus including an ink jet head having a plurality of
ejecting ports arranged in a predetermined pattern and a plurality of heat
generating elements arranged corresponding to said ejecting ports, and
driving controlling means applying a driving signal to said heat
generating elements in response to a driving information so as to allow
said heat generating elements to generate heat to generate bubbles from
ink and to defoam wherein a print ejecting mode for printing a printing
medium by ejecting ink from said ejecting ports and a preliminary ejecting
mode for performing no ejection toward said printing medium are settled
for said apparatus, characterized in that said driving controlling means
includes defoaming position changing means for changing the position of a
defoaming point while said apparatus is operated in conformity with said
preliminary ejecting mode.
2. An ink jet apparatus as claimed in claim 1, characterized in that said
driving signal is composed of a prepulse, a main pulse, and a pause time
between said prepulse and said main pulse, and that said defoaming
position changing means performs ejection by modulating at least one of
said prepulse and said pause time by two steps or more so as to change the
position of said defoaming point.
3. An ink jet apparatus including an ink jet head having a plurality of
ejecting ports arranged in a predetermined pattern and a plurality of heat
generating elements arranged corresponding to said ejecting ports, and
driving controlling means applying a driving signal to said heat
generating elements in response to a driving information so as to allow
said heat generating elements to generate heat to generate bubbles from
ink and to deform wherein a print ejecting mode for printing a printing
medium by ejecting ink from said ejecting ports and a preliminary ejecting
mode for performing no ejection toward said printing medium are settled
for said apparatus, characterized in that said driving and controlling
means includes ink adhering ingredient depositing means for allowing a
predetermined quantity of ink adhering ingredient to be preliminarily
adhesively deposited on said heat generating elements in conformity with
said preliminary ejecting mode, and ink adhering ingredient peeling means
for peeling said ink adhering ingredient on said heat generating elements
deposited by said ink adhering ingredient depositing means.
4. An ink jet apparatus as claimed in claim 3, characterized in that said
ink adhering ingredient depositing means changes and drives at least one
of a width of driving signal, a driving voltage and a driving cycle in
such a manner that a maximum reached point temperature of the surface of
each heat generating element coming in contact with ink is relatively
heightened,
and that said ink adhering ingredient peeling means changes and drives at
least one of a width of driving signal, a driving voltage and a driving
cycle in such a manner that a maximum reached temperature of the surface
of each heat generating element coming in contact with ink is relatively
lowered.
5. An ink jet apparatus as claimed in claim 4, characterized in that a sum
P.sub.W1 of a width of prepulse and a width of main pulse of said driving
signal applied to said heat generating elements by said ink adhering
ingredient depositing means and a sum P.sub.W2 of a width of prepulse and
a width of main pulse of said driving signal applied to said heat
generating elements by said ink adhering ingredient peeling means satisfy
the relationship represented by the following inequality.
1.1.times.P.sub.W1 .ltoreq.P.sub.W2 .ltoreq.2.5.times.P.sub.W1
6. An ink jet apparatus as claimed in claim 4 or claim 5, characterized in
that a cycle F.sub.q1 that said ink adhering depositing means applies a
driving signal to a same heat generating element and a cycle F.sub.q2 that
said ink adhering ingredient peeling means applies a driving signal to a
same heat generating element satisfy the relationship represented by the
following inequality.
F.sub.q1 <F.sub.q2
7. An ink jet apparatus including an ink jet head having a plurality of
ejecting ports arranged in a predetermined pattern and a plurality of heat
generating elements arranged corresponding to said ejecting ports, and
driving controlling means applying a driving signal to said heat
generating elements in response to a driving information so as to allow
said heat generating elements to generate heat to generate bubbles from
ink and to defoam wherein a print ejecting mode for printing a printing
medium by ejecting ink from said ejecting ports and a preliminary ejecting
mode for performing no ejection toward said printing medium are settled
for said apparatus, characterized in that said driving controlling means
includes ink adhering depositing means for allowing a predetermined
quantity of ink adhering ingredient to be preliminarily deposited on said
heat generating elements in conformity with said preliminary ejecting
mode, ink adhering ingredient peeling means for peeling said ink adhering
ingredient on each heat generating element deposited by said ink adhering
ingredient depositing means, and heat generating element usage state
capturing means for capturing the usage state of each heat generating
element or dividing said heat generating elements into at least two groups
to capture the usage state of each of divided heat generating elements,
and
that said driving signal is controlled in conformity with said preliminary
ejecting mode based on the usage state captured by said heat generating
element usage state capturing means.
8. An ink jet apparatus as claimed in claim 7, characterized in that said
heat generating element usage state capturing means includes printing dot
counting means, counting means for counting a printing time, and means for
seeking a printing duty, and that the usage state of each heat generating
element is captured by said means for seeking a printing duty.
9. An ink preliminary ejecting method to be practiced by an ink jet
apparatus including an ink jet head having a plurality of ejecting ports
arranged in a predetermined pattern and a plurality of heat generating
elements arranged corresponding to said ejecting ports, and driving
controlling means applying a driving signal to said heat generating
elements in response to a driving information so as to allow said heat
generating elements to generate heat to generate bubbles from ink and to
defoam wherein a print ejecting mode for printing a printing medium by
ejecting ink from said ejecting ports and a preliminary ejecting mode for
performing no ejection toward said printing medium are settled for said
apparatus, characterized in that said preliminary ejecting mode includes a
first preliminary ejecting step of allowing a predetermined quantity of
ink adhering ingredient to be deposited on each heat generating element
and a second preliminary adhering step of peeling from said heat
generating elements an ink adhering ingredient adhesively deposited by
practicing said first preliminary ejecting step.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ink jet apparatus for conducting
printing ejection for a printing medium by ejecting ink from ejection
ports as well as conducting preliminary ejection without any printing on
the printing medium.
2. Description of the Related Art
Various kind of recording apparatus such as printer, copying machine,
facsimile and so forth is constructed such that character and image each
composed of dot pattern are printed on a printing medium such as a sheet
of paper, a sheet of plastic thin plate or the like in response to
character information or image information.
The recording apparatus can be classified into an ink jet system, a wire
dot system, a thermal system, a laser beam system in terms of a recording
system.
Among them, the ink jet system is such that each printing operation is
performed by ejecting ink from an ink jet head to a printing medium, and
has advantages that an image having excellent finesse can be printed at
high speed, since the ink jet system is no impact system, few nosy sound
is generated during printing operation, and moreover, colored image can
easily be printed on the printing medium using multicolored inks.
Especially, a system wherein a heat generating element is used as an
ejection energy generating element for generating energy for ejecting ink
therefrom has advantages that a head can be designed with small dimensions
and recording can be achieved with high fineness.
With respect to an ink jet system having a heat generating element used
therefor, there sometimes arises an occasion that part of dyestuff,
pigment or the like is thermally decomposed on the heat generating element
depending on the kind of ink, the state of usage of the head or the like,
causing the decomposed substance to be adhesively deposited on the heat
generating element. Due to the fact that an intensity of ink ejecting
force is lowered because of the presence of adhering ingredient
(hereinafter referred to as ink adhering ingredient), causing no normal
ejection to be conducted, and moreover, a quantity of ink adhering
ingredient differs among a plurality of heat generating elements, causing
ink ejecting force to differ for each of heat generating elements, there
is a danger that density fluctuation arises with formed character or
image. Namely, with a conventional ink jet apparatus, there arises an
occasion that the kind of available ink is restricted in order to
accomplish a high quality of printing, and moreover, density fluctuation
arises with character or image to be formed due to a difference of usage
of the heat generating element.
Conventionally, the following measures have been proposed as a method of
removing the adhesively deposited material on a heat generating element by
the cavitation arising at the time when a foam caused by the heat
generated by the heat generating element disappears, with respect to
printing density fluctuation caused by the adhesive deposition. (1) Foams
are repeatedly formed while part or the whole of ejection ports of an ink
jet head is kept closed. (2) Preliminary ejection is performed using all
the heat generating elements with a constant width of driving signal and a
constant driving cycle. (3) Means for counting the number of usage of
every heat generating element is disposed and the number of times of
preliminary ejection is changed with respect to each of heat generating
elements. (4) Pulse width modulation control (PWM control) is performed in
conformity with a printing ejection mode of printing a printing medium by
ejecting ink from ejection ports.
Among the conventional measures for removing density fluctuation of
character, image or the like by adhesively depositing of ink adhering
element on the heat generating element,
with the measure shown in the paragraph (1), the defoaming position can be
changed depending on a manner of closing the ejecting ports, but since it
is very difficult to control the manner of closing the ejecting ports, it
is also difficult that ink adhering ingredient present in the wide range
on the heat generating element is sufficiently removed. In addition, after
processing is performed, ink adheres to the ejection port plane of the ink
jet head. Thus, it is necessary to perform recovering treatment for
removing the adhering ink. Since foam is generated while the ejecting
ports are kept closed, bubble remaining after defoaming stays in ink jet
head. Therefore, there is a danger that the staying bubble becomes a
factor of incorrect printing (ejection of foam, warpage of ink ejection)
unless recovering treatment is performed.
With the measure explained in the paragraph (2), since preliminary ejection
is performed with a constant width of driving signal and a constant
driving cycle, ink adhering ingredient present in the wide range on the
heating element can not sufficiently be removed. Indeed, it is difficult
to eliminate a difference in a quantity of ink adhering ingredient with
respect to each of heat generating elements. For this reason, density
fluctuation of character, image or the like can not sufficiently be
eliminated. A problem to be solved is that a quantity of ink to be used
for preliminary ejection becomes very large.
With the measure shown in the paragraph (3), a difference in a quantity of
ink adhering ingredient between respective heat generating elements can be
eliminated. However, another problem to be solved is that a quantity of
consumption of ink to be used for preliminary ejection is still large.
The PMW controlling method shown in the paragraph (4) is practiced to
modulate the pulse width corresponding to the temperature of the ink jet
head, and moreover, to maintain a quantity of ink ejection at the time of
printing ejection constant. As one example, the driving signal is divided
into two (prepulse and main pulse) and the pause time of prepulse and main
pulse is modulated. However, the PWM controlling method is a controlling
method for maintaining a quantity of ink ejection constant by shortening
the pause time when the ink jet head has a higher temperature and
elongating the pause time when the ink jet head has a lower temperature.
Therefore, since the defoaming position on the heat generating element is
dependent on a quantity of ink ejection, the defoaming position does not
large vary. Namely, with the PWM controlling method at the time of
printing ejection, the ink adhering ingredient dispersively deposited on
the heat generating element can not sufficiently be removed.
OBJECT OF THE INVENTION
An object of the present invention is to provide an ink jet apparatus which
assures that density fluctuation in character, image or the like can be
eliminated ad which makes it possible to reduce a quantity of ink to be
used for preliminary ejection compared with a conventional ink jet
apparatus.
In addition, other object of the present invention is to provide an ink
preliminary ejecting method to be practices by the ink jet apparatus which
assures that density fluctuation in character, image or the like can be
eliminated and which makes it possible to reduce a quantity of consumption
of ink to be used for preliminary ejection compared with the conventional
ink jet apparatus.
SUMMARY OF THE INVENTION
According to a first aspect of the present invention, there is provided an
ink jet apparatus including an ink jet head having a plurality of ejecting
ports arranged in a predetermined pattern and a plurality of heat
generating elements arrange corresponding to the ejecting ports, and
driving controlling means for applying a driving signal to the heat
generating elements in response to a driving information so as to allow
the heat generating element to generate heat to generate bubbles from ink
and to defoam wherein a printing ejecting mode for printing a printing
medium by ejecting ink from the ejecting ports and a preliminary ejecting
mode for performing no ejection toward the printing medium are settled for
the apparatus, characterized in that the driving controlling means
includes defoaming position changing means for changing the position of a
defoaming point while the apparatus is operated in conformity with the
preliminary ejecting mode.
The driving signal is composed of a prepulse, a main pulse, and a pause
time between the prepulse and the main pulse, and it is preferable that
the defoaming position changing means performs ejection by modulating at
least one of the prepulse and the pause time by two steps or more so as to
change the position of a deforming point.
According to a second aspect of the present invention, there is provided an
ink jet apparatus including an ink jet head having a plurality of ejecting
ports arranged in a predetermined pattern and a plurality of heat
generating elements arranged corresponding to the ejecting ports, and
driving controlling means applying a driving signal to the heat generating
elements in response to a driving information so as to allow the heating
elements to generate heat to generate bubble from ink and to defoam
wherein a print ejecting mode for printing a printing medium by ejecting
ink from the ejecting ports and a preliminary ejecting mode for performing
no ejection toward the printing medium are settled for the apparatus,
characterized in that the driving controlling means includes ink adhering
ingredient depositing means for allowing a predetermined quantity of ink
adhering ingredient to be preliminarily deposited on the heat generating
elements in conformity with the preliminary ejecting mode and ink adhering
ingredient peeling means for peeling the ink adhering ingredient on the
heat generating elements deposited by the ink adhering ingredient
depositing means,
It is preferable that the ink adhering ingredient depositing means changes
and drives at least one of a width of driving signal, a driving voltage
and a driving cycle in such a manner that a maximum reached temperature of
the surface of each heat generating element coming in contact with ink is
relatively heightened. In this case, it is effective that a sum P.sub.W1
of a width of prepulse and a width of main pulse of the driving signal
applied to the heat generating elements by the ink adhering ingredient
depositing means and a sum P.sub.W2 of a width of prepulse and a width of
main pulse of the driving signal applied to the heat generating elements
by the adhering ingredient peeling means satisfy the relationship
represented by the following inequality.
1.1.times.P.sub.W1 .ltoreq.P.sub.W2 .ltoreq.2.5.times.P.sub.W1
and, it is effective that a cycle F.sub.q1 that the ink
adhering depositing means applies a driving signal to a same heating
element and a cycle F.sub.q2 that the ink adhering ingredient peeling
means applies a driving signal to a same heat generating element satisfy
the relationship represented by the following inequality
F.sub.q1 <F.sub.q2
In addition, according to the third aspect of the present invention, there
is provided an ink jet apparatus including an ink jet head having a
plurality of ejecting ports arranged in a predetermined pattern and a
plurality of heat generating element arranged corresponding to the
ejecting ports, and driving controlling means applying a driving signal to
said heat generating elements in response to a driving information so as
to allow the heat generating elements to generate heat to generate bubble
from ink and to defoam wherein a printing ejecting mode for printing
medium by ejecting ink from the ejecting ports and a preliminary ejecting
mode for performing no ejection toward the printing medium are settled for
the apparatus, characterized in that the driving controlling means
includes ink adhering depositing means for allowing a predetermined
quantity of ink adhering ingredient to be preliminarily deposited on the
heat generating elements in conformity with the preliminary ejecting mode,
ink adhering ingredient peeling means for peeling the ink adhering
ingredient on each heat generating element deposited by the ink adhering
ingredient depositing means, and a heat generating element usage state
capturing means for capturing the usage state of each heat generating
element or dividing the heat generating elements into two groups to
capture the usage state of each of divided heat generating elements, and
that the driving signal is controlled in conformity with the preliminary
ejecting mode based on the usage state captured by the heat generating
element usage capturing means.
It is preferable that the heating element usage state capturing means
includes printing dot counting means, counting means for counting a
printing time, and means for seeking a printing duty, and that the usage
state of the heating element is captured by the means for seeking a
printing duty.
Further, according to the fourth aspect of the present invention, there is
provided an ink preliminary ejecting method to be practiced by an ink jet
apparatus including an ink jet head having a plurality of ejecting ports
arranged in a predetermined pattern and a plurality of heat generating
elements arranged corresponding to the ejecting ports, and driving
controlling means applying a driving signal to the heat generating
elements in response to a driving information so as to allow the heat
driving elements to generate heat to generate bubbles from ink and to
defoam wherein a printing ejecting mode for printing a printing medium by
ejecting ink from the ejecting ports and a preliminary ejecting mode for
performing no ejection toward the printing medium are settled for the
apparatus, characterized in that the preliminary ejecting mode includes a
first preliminary ejecting step of allowing a predetermined quantity of
ink adhering ingredient to be deposited on each heating element and a
second preliminary adhering step of peeling from the heat generating
elements an ink adhering ingredient adhesively deposited by practicing the
first preliminary ejecting step.
According to the first aspect of the present invention, it is possible to
change the position of cavitation induced on the heat generating element
at the time of defoaming. In other words, the ink adhering ingredient
dispersively deposited can be peeled from the whole surface of the heat
generating elements.
According to second aspect and the fourth aspect, by peeling the ink
adhering ingredient from the heat generating element by the ink adhering
ingredient peeling means after the ink adhering ingredient is
preliminarily adhesively deposited on the whole surface of the heat
generating element with the aid of the ink adhering ingredient depositing
means, the ink adhering ingredient can be peeled at a higher efficiency
than the case that the ink adhering ingredient partially adhesively
deposited on the heat generating element can be peeled.
According to the third aspect, a quantity of ink adhering ingredient
deposited on the heat generating elements can be presumed by capturing the
usage state of the heat generating elements, and since optimum preliminary
ejection can be executed for each heat generating element, ink adhering
ingredient can be removed with a minimum quantity of ink consumption
without any deterioration of running life of the heat generating elements.
The above and other objects, effects, features and advantages of the
present invention will become more apparent from the following description
of embodiments thereof taken in conjunction with the accompanying drawings
.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view which schematically shows the structure of an
embodiment wherein an ink jet apparatus of the present invention is
applied to a printer.
FIG. 2 is a fragmentary enlarged perspective view which shows an ink jet
head shown in FIG. 1.
FIG. 3 is a control block diagram in the embodiment shown in FIG. 1 and
FIG. 2.
FIG. 4 is a circuit diagram which shows a part of the control block shown
in FIG. 3.
FIG. 5 is a control block diagram of a first concrete example in this
embodiment.
FIG. 6 is a sectional view of the fore end part of an ink jet head which
represents the relationship between a preliminary ejection and a defoaming
point in the first concrete example.
FIG. 7 is a flowchart which represents a series of steps for line feed
interruption in the first concrete example.
FIG. 8 is a flowchart which represents a series of steps for a 50
millisecond interruption processings in the first concrete example.
FIG. 9 is a control block diagram of a second concrete example in this
embodiment.
FIG. 10A-10E are schematic views which represents adhering deposition of
ink adhering ingredient of an ink adhering ingredient on the surface of a
heat generating element in an ink passage.
FIG. 11 is a flowchart which represents a series of steps for line feed
interruption processings in the second concrete example in this
embodiment.
FIG. 12 is a control block diagram of a third embodiment in this
embodiment.
FIG. 13 is a flowchart which represents a series of steps of line feed
interruption processings in the third concrete example.
FIG. 14 is a flowchart which represents a series of steps of 50 millisecond
interruption processing in the third concrete example.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The present invention will now be described in detail hereinafter with
reference to FIG. 1 to FIG. 14 with respect to an embodiment wherein an
ink jet apparatus of the present invention is applied to an ink jet
printer.
As shown in FIG. 1 which represents an appearance of the ink jet printer of
this embodiment, as normal and reverse rotation of a driving motor 11 is
transmitted to a feed screw 5 via two driving power transmitting gears 9
and 10, a carriage 2 is reciprocably displaced in a arrow-marked direction
or in the b arrow-marked direction, An ink jet cartridge 1 integrated with
an ink jet head 18 (see FIG. 2) for ejecting ink toward a printing medium
30 such as a sheet of paper or the like and an ink tank having a printing
ink received therein is mounted on a carriage 2. In addition, a platen 4
for conveying the printing medium 30 is rotatably arranged while facing to
the ink jet cartridge 1.
The printing medium 30 conveyed by the platen 4 is thrusted against the
platen by a paper retainer 3, and moreover, it is held in such a manner as
to maintain a predetermined gap between the printing medium 30 and the ink
jet cartridge 1. A printing operation for ejecting ink from the ink jet
head 18 while displacing the carriage 2 with the aid of the driving motor
11 is performed under control of a print controlling means 22. At this
time, the number of printed dots is counted by counting means 25. A
temperature sensor 21 for measuring the temperature of the ink jet head 18
is attached to the ink jet head 8 for the ink jet cartridge so that a
quantity of electricity corresponding to the measured temperature is
outputted to suction operation controlling means 23.
It should be noted that the temperature sensor 21 is not always required
and the temperature sensor 21 is attached to the ink jet head 1 but any
type temperature sensor can be attached to the ink jet apparatus at an
arbitrary position, provided that it is proven that the temperature of the
ink jet head 18 can be presumed.
Two photocouplers 7 and 8 are disposed on the left-hand side as viewed in
the displacing direction of the carriage 2. The photocouplers 7 and 8
serve as home position detecting means for confirming that a lever
disposed at the left-hand end of the carriage 2 is present in the range
including the photocouplers 7 and 8 and then shifting the direction of
rotation of the driving motor 11. In addition, a capping member 13
supported by a cap supporting member 14 is disposed at the position where
the ink jet cartridge 1 is displaced at the time of sucking operation
outside the range that the ink jet cartridge 1 is reciprocably displaced
during printing operation. The capping member 13 is intended to cap the
whole ejecting outlet plane 1a (see FIG. 2) of the ink jet head 18
therewith, and while the injecting head 18 is completely capped with the
capping member 13, ink having increased viscosity and bubbles remaining in
the ink jet head 18 are removed from the injecting head 18 so as to
conduct receiving operation.
A cleaning blade 25 supported by a blade supporting member 16 is disposed
sideward of the capping member 13. The cleaning blade 15 is supported so
as to enable to project toward the ink cartridge 1 until it comes in
contact with the ink jet head 18. Thus, after completion of a sucking
operation, the cleaning blade is projected toward the moving path of the
ink jet cartridge 1 to wipe off dirty material on the front surface of the
ink jet head 18 as the ink jet cartridge is displaced. The cleaning blade
25 should not be limited only this type, and it is acceptable that other
hitherto known cleaning blade is employed for the same purpose.
As shown in FIG. 2 that is a fragmentary enlarged view of the ink jet head
18, a plurality of ejecting ports 1b are formed on the ejecting port plane
1a facing to the printing medium 30 (see FIG. 1) with a predetermined gap
therebetween and with a predetermined pitch, and a plurality of heat
generating elements 1e(electrothermal transducers used in this embodiment)
each serving to generate thermal energy for ink ejection are arranged
along wall surfaces of ink paths 1d by way of which a common ink chamber
1c is communicated with each ejecting port 1b. The common ink chamber 1c
is communicated with the ink tank of the ink jet cartridge 1 (see FIG. 1)
so that ink is supplied to the ink tank from the common ink chamber 1c.
The ink supplied from the ink tank to the common ink chamber 1c and
temporarily stored in the common ink chamber 1c maintains the state that
an ink path 1d is filled with ink under the influence of a capillary
phenomenon. When electricity is fed to the heat generating element 1e and
heat is generated with the printing element 1e via an electrode (not
shown), ink exposed to the heat generating element 1e is quickly heated to
generate bubbles in the ink tank 1d attributable to an appearance of a
phenomenon of film boiling, and as the bubbles are generated, ink is
ejected from the ejecting ports 1d.
FIG. 3 shows the block structure including controlling means 49 in this
embodiment. In detail, reference numeral 41 denotes an interface into
which a printing signal is inputted, and reference numeral 42 denotes a
microprocessor (hereinafter referred to as MPU). Reference numeral 43
denotes a program ROM in which a control program to be executed by MPU 42
is stored, reference numeral 44 denotes a DRAM in which various data such
as a printing signal, printing data to be fed to the ink jet head 18 and
so forth is reserved. The number of printed dots, the number of
replacements of the ink jet head 18 and so forth can be stored in DRAM 44.
Reference numeral 45 denotes a gate array for controllably supply printing
data to the ink jet head 18 so as to allow data to be controllably
transferred among the interface 41, the MPU 42 and the DRAM 44. Reference
numeral 20 denotes a carrier motor for conveying the ink jet head 18, and
reference numeral 19 denotes a conveyance motor for conveying a printing
paper. Reference numeral 46 denotes a head driver for driving the ink jet
head 18, and reference numerals 47 and 48 denote motor driver for driving
the conveyance motor 19 and carrier motor 20.
FIG. 4 shows a part of circuits of the controlling means shown in FIG. 30.
Specifically, the gate array 45 includes a data latch 141, a segment shift
register 142, a multiplexer 143, a common timing generating circuit 144
and a decoder 145. The ink jet head 18 is constructed in the form of a
diode matrix, and when a common signal COM and a segment signal SEG match
with each other, a driving current flows to heat generating elements 1e
(in this embodiment, E.sub.1 to E.sub.128) so that ink is heated and
ejected to each ejecting port 1b.
The decoder 145 decodes a timing generated by a common timing generating
circuit 144 and selects one of common signals COM1 to COM16. The data
latch 141 latches the printing data read from DRAM with eight bit in unit,
and the multiplexer 143 follows a segment shift register 142 in conformity
with the print data to output the print data as segment signals SEG1 to 8.
The output from the multiplexer 143 can variously be changed depending on
the content of the segment shift register 142 with one bit in unit, with
two bits in unit or with eight bits in unit.
Operations of the controlling means will be described below. Namely, when a
printing signal is inputted into the interface 41, the printing signal is
converted into printing data between the gate array 45 and the MPU 42.
Then, motor drivers 47 and 48 are driven, and the ink jet head 18 is
driven in conformity with the printing data sent from the head driver 46
so that a printing operation is performed.
Here, description will be made below with respect to an example wherein ink
adhering ingredient adhesively deposited on a heat generating element 1e
is removed by modulating a driving signal of preliminary ejection by
multi-steps (hereinafter referred to as a first concrete example).
During a normal printing operation, a predetermined ink adhering ingredient
is deposited on the heat generating element 1e corresponding to the state
of usage (the kind of ink, the number of heating, a driving frequency, a
driving pulse and so forth). Generally, there is a tendency that a
quantity of ink adhering ingredient adhesively deposited on the heat
generating element is increased more and more as a driving frequency is
higher and a driving pulse is larger. The reason for this consists in that
the maximum temperature which can be reached by the heat generating
element 1e is high. As ink adhering ingredient is increasingly deposited
on the heat generating element 1e, uniform film bolding does not arise
with the heat generating element Ie. As a result, an intensity of ink
ejecting force is reduced and a quantity of ink ejection is reduced. With
respect to the ink adhering ingredient adhesively deposited on the heat
generating element 1e, the ink adhering components located in the vicinity
of a defoaming point peels due to such cavitation that the surrounding ink
collides against the heat generating element 1e during defoaming.
Therefore, during normal printing, deposition and peeling of the ink
adhering ingredient are repeated on the heat generating element 1e, and a
quantity of ink ejection always varies.
In the case of an ink jet printing apparatus including a plurality of heat
generating elements 1e and having such a structure that a certain specific
heat generating element group A and another specific heat generating
element group B are separately used, periodical deviation arises between a
quantity of deposition of the ink adhering ingredient of the heat
generating element group A and that of the heat generating element group
B, and in the case that an image is formed by simultaneously ejecting the
heat generating element group A and the heat generating element group B,
density fluctuation appears.
According to the preset invention, to obviate the density fluctuation, a
measure is taken such that the defoaming point on the heat generating
element 1e deviated by modulating the driving signal at the time of
preliminary ejection, and moreover, the ink adhering element within the
wide range of the surface of the heat generating element 1e is peeled.
FIG. 5 shows schematic structure of a block of the present invention, Here,
the driving controlling means 50 includes a deforming position changing
means 53 for changing the defoaming position of the heat generating
element 1e in the ink jet head 18, and performs driving controlling for
the heat generating element 1e with a predetermined driving signal, and at
a redetermined cycle and a predetermined number of times in conformity
with a preliminary ejecting mode.
Table 1 shows preliminary ejecting conditions employed for this embodiment.
TABLE 1
______________________________________
main
driving prepulse pause pulse number
frequency
width time width of
(Hz) (.mu.s) (.mu.s) (.mu.s)
pulses
______________________________________
preliminary
500 1.0 0.0 4.2 100
ejection A
preliminary
500 1.0 0.0 4.3 100
ejection B
preliminary
500 1.0 1.8 4.2 100
ejection C
preliminary
500 1.0 2.7 4.2 100
ejection D
______________________________________
FIG. 6 shows positional deviation of the defoaming point when preliminary
ejection A to preliminary ejection D are successively conducted. As is
apparent from FIG. 6, as the width of the pause time is increased, the
defoaming point P.sub.B shifts from the ejecting port 1b to the position
away from the former. This means that as a width of the pause time is
enlarged, a quantity of ejection of ink increased and a quantity of ink
remaining from the central position of the heat generating element 1e to
the ejection port 1b side is reduced, resulting in the ink being pulled in
the opposite direction to the ejecting port 1b.
When preliminary ejection is performed while the preliminary ejection A to
the preliminary ejection D are taken as a series of preliminary ejecting
operations, the position where cavitation occurs on the heat generating
element 1e is displaced, whereby it becomes possible to peel the ink
adhering ingredient within the wide range on the heat generating element
1e. Thus, it is possible to obviate density fluctuation by keeping a
quantity of ejection between the heat generating element 1e constant but
depending on the frequency of usage of the heat generating element 1e.
The preliminary ejection for peeling the ink adhering ingredient makes it
possible to reduce a quantity of consumption of ink by warpage of ink
ejection during printing operation due to fixing of the ink adhering
ingredient to the ink passage 1d and vaporization of water from the
surface M.sub.F of the meniscus or by ejecting ink at a timing for
preliminary ejection for the purpose of preliminarily preventing the
failure of ink ejection. Concretely, preliminary ejection can be performed
when a predetermined number of dots can be counted with the aid of
disposed dot counting means or it can be performed with the aid of
counting means for counting the printing operation when a predetermined
time elapses. In addition, it is acceptable that a preliminary ejecting
distance is changed or a predetermined cycle of time is changed by using
means for presuming or detecting the temperature of the ink jet head. It
is preferable that the ink jet head is ready to stably perform printing
operation using the ink jet head.
FIG. 7 and FIG. 8 show a series of steps to be practiced for preliminary
ejection in accordance with this embodiment. FIG. 7 shows a line
interruption subroutine to be executed every time line is changed, and
FIG. 8 shows a 50 millisecond interruption subroutine to be executed every
50 milliseconds. In this embodiment, the aforementioned preliminary
ejections A to D are practiced every five seconds at the time of printing
operation and at the time of standby that the capping member 13 is parted
away from the ejecting port plane 1a, and moreover, they are practiced
after completion of wiping operation in the case that the number of
printed dots exceeds a predetermined one.
In a step of line feed interruption shown in FIG. 7, it is determined
whether or not preliminary ejection flag F.sub.1 and wiping flag F.sub.w
are set to 1. In the case that it is found that the wiping flag is set to
1, wiping operation is performed, and subsequently, preliminary ejections
A to D are performed. After completion of each processing, flag is reset
to 0 and timer counting value C.sub.r is reset to 0. Namely, it is
determined in Step S11 whether or not wiping flag F.sub.W is set to 1 and
in the case that it is determined that it is set to 1, the subroutine goes
to Step S12 in which wiping operation is performed. Subsequently, in Step
S13, wiping flag F.sub.w is reset to 0, and moreover, in Step S14, timer
counting value C.sub.r is reset to 0. The subroutine goes to Step S15 to
Step S18 in which preliminary ejections A to D are successively performed,
and thereafter, at Step S19, preliminary ejecting flag F.sub.1 is reset to
0, and moreover, in Step S20, total printed dot number N.sub.p is reset to
0, whereby interruption processing is completed.
On the other hand, in the case that it is determined in Step S11 that
wiping flag F.sub.w is not set to 1, the subroutine goes to Step 21 in
which it is determined whether preliminary ejecting flag F.sub.1 is set to
1 or not. In the case that it is found that preliminary flag F.sub.1 is
set to 1, the subroutine goes to Step S15 and subsequent ones. However, in
the case that it is determined that preliminary ejecting flag F.sub.1 is
reset to 0, interruption processing is completed while nothing is done.
On the other hand, in the 50 millisecond interruption shown in FIG. 8,
timer counts for five seconds and the number of printed dots is counted.
In the case that the result derived from each counting exceeds a specified
value, preliminary ejecting flag F.sub.1 and wiping flag F.sub.w are set
to 1, respectively. Namely, in Step 31, timer count value C.sub.T is
increased by one and the subroutine goes to Step 32 in which it is
determined whether the count value C.sub.r exceeds 100 or not. In the case
that it is determined that the timer count value C.sub.r exceeds 100, the
subroutine goes to Step S33 in which preliminary flag F.sub.1 is set to 1,
and thereafter, the subroutine goes to Step S33 in which preliminary
ejecting flag F1 is set to 1, and thereafter, in Step S34, the number of
printed dot number N.sub.d for 50 milliseconds till now is read and the
subroutine goes to Step S35 in which the total printed dot number N.sub.D
till this time is calculated in accordance with the following equation.
N.sub.D =N.sub.D +N.sub.d
In step S36, it is determined whether the total printed dot number N.sub.D
is larger than 1.5.times.10.sup.5 or not. In the case that it is
determined the total printed dot number N.sub.D is larger than
1.5.times.10.sup.5, the subroutine goes to Step S37 in which wiping flag
F.sub.W is set to 1, whereby this interruption processing is completed.
In the case that it is determined in Step S32 that timer count value
C.sub.T is 100 or less, the subroutine goes to Step S34 and subsequent
ones, and in the case that it is determined in Step S36 that total printed
dot number N.sub.D is 1.5.times.10.sup.5 or less, this interruption
processing is terminated.
In this embodiment, it is preferable that driving frequency for preliminary
ejection is set to a possibly low frequency in order to prevent ink
adhering ingredient from being deposited on the heat generating element 1e
by preliminary ejection. It is desirable that the preliminary ejecting
conditions noted in Table 1 are set to optimum ones based on ink
composition or ink jet head structure. However, the present invention
should not be limited to the aforementioned preliminary ejecting
conditions.
Next, description will be made below with respect to an embodiment wherein
a sum of width of first preliminary ejecting prepulse and width of main
pulse is relatively larger than a sum of width of second preliminary
prepulse and width of main pulse so as to remove ink adhering ingredient
on the heat generating element 1e and eliminate the density fluctuation
(hereinafter referred to a second concrete embodiment).
As shown in FIG. 9 which represents the structure of this concrete example,
driving controlling means 50 includes ink adhering depositing means 51 ad
ink adhering ingredient peeling means 52 and drives and controls the heat
generating element 1e in the ink jet head 1e in the following manner.
Specifically, in this complete example, first preliminary ejection for
depositing ink adhering ingredient and second preliminary ejection for
peeling the ink adhering ingredient are conducted. Since a sum of width of
first preliminary ejection and width of main pulse is relatively larger
than a sum of width of prepulse of second preliminary ejection and width
of main pulse, ink adhering ingredient on the heat generating element 1e
can be removed and density fluctuation can be eliminated.
As described above with respect to the first concrete example, the ink
adhering ingredient deposited on the heat generating element at the time
of printing is repeatedly subjected to depositing and peeling. FIG.
10A-10E schematically show ink adhering ingredient on heat generating
element at a certain time point of printing operation. FIG. 10A shows the
initial state of the heat generating element 1e. As shown in FIG. 10B and
FIG. 10C, ink adhering ingredient I.sub.s at a certain time point is
irregularly adhesively deposited on the surface of the heat generating
element 1e, and the state of adhesive deposition of ink adhering
ingredient I.sub.s varies depending on the history of usage of the heat
generating element 1e. A constant quantity of ink adhering ingredient
I.sub.s uniformly deposited on the heat generating element 1e shown in
FIG. 10D has a possibility that peeling of the ink adhering ingredient
I.sub.s arises attributable to cavitation at the time of defoaming over
the wide range on the surface of the heat generating element as shown in
FIG. 10E. This has been clarified by a variety of reviews conducted by the
inventors.
Namely, as shown in FIG. 10B and FIG. 10C, it is clarified that ink
adhering ingredient I.sub.s uniformly distributed as shown in FIG. 10D is
readily peeled from the surface of the heat generating element 1e rather
than the ink adhering ingredient I.sub.s irregularly distributed on the
heat generating element 1e. According to the present invention, the ink
adhering ingredient I.sub.s is not substantially deposited on the surface
of the heat generating element 1e by uniformly depositing ink adhering
ingredient I.sub.s on the surface of the heat generating element 1e by the
first preliminary ejection as shown in FIG. 10D and then by peeling the
ink adhering ingredient I.sub.s deposited on the surface of the heat
generating element Ie by the second preliminary ejection as shown in FIG.
10E, whereby the reduction of a quantity of ejection of ink due to the ink
adhering ingredient I.sub.s is prevented, and moreover, the density
fluctuation is prevented.
Driving conditions associated with the first preliminary ejection
(preliminary ejection 1) and the second preliminary ejection (preliminary
ejection 2a, preliminary ejection 2b and preliminary ejection 2c) as
mentioned above are shown on Table 2.
TABLE 2
______________________________________
width
driving width of pause of main
number
frequency prepulse time pulse of
(Hz) (.mu.s) (.mu.s) (.mu.s)
pulse
______________________________________
preliminary
6.25 .times. 1000
1.0 0.0 8.62 1000
ejection 1
preliminary
500 1.0 0.0 4.2 300
ejection 2a
preliminary
500 1.0 0.9 4.2 300
ejection 2b
preliminary
500 1.0 1.8 4.2 300
ejection 2c
______________________________________
The preliminary ejection 1 is a preliminary ejection for assuring that ink
adhering ingredient I.sub.s is uniformly deposited on the heat generating
element 1e, and the preliminary ejection 2a to the preliminary ejection 2c
are a preliminary ejection for assuring that the ink adhering ingredient
I.sub.s deposited on the heat generating element 1e by the preliminary
ejection 1 is removed, respectively.
Deposition of the ink adhering ingredient I.sub.s on the heat generating
element 1a by the preliminary ejection 1 is readily achieved more and more
as the driving frequency is higher, and moreover, a sum of width of
prepulse and width of main pulse is larger. Therefore, a quantity of
consumption of ink can be reduced by elongating the pulse width with high
driving frequency. However, it is preferable in consideration of
durability of the heat generating element 1e that the quantity of
consumption of ink is determined within the range where any inconvenience
does not arise in practical use.
As described above with respect to the first concrete example, the
preliminary ejection 2a to the preliminary ejection 2c change a quantity
of ejection by modulating the pause time, and it is possible to remove the
ink adhering Ingredient I.sub.s on the heat generating element 1e within
the whole range by shifting on the heat generating element 1e the position
of cavitation caused by changing of the quantity of ejection. Here, the
width of pause time has been modulated to enhance the effect, but since
the ink adhering ingredient I.sub.s deposited by the preliminary ejection
is readily peeled, good results are obtainable without any necessity for
modulating the width of pause time.
FIG. 11 shows a series of steps of preliminary ejection processings in
accordance with this embodiment. FIG. 11 illustrates a line feed
interruption subroutine to be practiced every time line is changed. With
this subroutine, it is determined whether or not preliminary ejection flag
F.sub.1 and wiping flag F.sub.w are set to 1. In the case that it is found
that the wiping flag is set to 1, wiping operation is performed, and
subsequently, preliminary ejections 1 to 2c are performed. After
completion of each processing, flag is reset to 0, and at the same time,
timer count value C.sub.T is reset to 0. In detail, it is determined in
Step S41 whether or not the wiping flag F.sub.W is set to 1, and in the
case that it is determined that it is set to 1, the routine goes to Step
S42 in which wiping operation is performed. Subsequently, in Step S43, the
wiping flag F.sub.w is reset to 0, and in Step S44, the timer count value
C.sub.r is reset to 0. After the subroutine successively goes to Step S45
to Step S48 to perform the preliminary ejection 1 to 2c, in Step S49,
preliminary ejection flag F.sub.1 is reset to 0, and subsequently, in Step
S50, a total printed dot number N.sub.D is reset to 0, whereby
interruption processings are terminated.
On the other hand, in the case it is determined in Step S41 that the wiping
flag F.sub.w is not set to 1, the subroutine goes to Step S51 in which is
determined whether or not the preliminary flag F1 is set to 1. In the case
that it is determined that the preliminary ejection flag F.sub.1 is set to
1, the subroutine goes to Step S45 and subsequent ones. In the case that
it is determined that the preliminary ejection flag F1 is reset to 0, the
interruption processing is terminated while nothing is done. With respect
to a method of setting the preliminary ejection flag F.sub.1 and wiping
flag F.sub.w, each setting is practiced in accordance with the 50
millisecond interruption subroutine as shown in FIG. 8.
In such manner, by adhesively depositing the ink adhering ingredient
I.sub.s on the heat generating element 1e by the first preliminary
ejection and peeling the ink adhering ingredient I.sub.s by the second
preliminary ejection, it becomes possible to remove the ink adhering
ingredient I.sub.s irregularly deposited on the heat generating element
1e. Thus, all the heat generating elements 1e each having different state
of usage can has a same quantity of ejection, and moreover, eliminate
density fluctuation. In addition, with ink which is readily deposited on
the heat generating element 1e and of which ejection quantity is
immediately reduced, according to the present invention, ink adhering
ingredient I.sub.s on the heat generating element 1e can be removed, and a
width of selection of ink can be widened much more than up to this time.
Next, description will be made below as to an example wherein a quantity of
ink adhering ingredient I.sub.s deposited on the surface of each of a
plurality of heat generating elements 1e is presumed with respect of each
of a group of heat generating elements so that density fluctuation is
further reduced by performing preliminary ejection corresponding to the
presumed quantity of deposited ink adhering ingredient (hereinafter
referred to as a third concrete example) I.sub.s. Here, to simplify
description, it is assumed that adjacent four heat generating elements 1e
are taken as one heat generating element group. FIG. 12 shows control
blocks wherein four groups of heat generating elements, i.e., an ink jet
head having sixteen ejecting ports 1b formed thereon is taken as an object
to be controlled.
Specifically, controlling means includes printing duty calculating means
58, time counting means 24, and dot counting means 25. The time counting
means 24 counts predetermined time. In this embodiment, the time counting
means 24 counts 10 seconds and the dot counting means 25 counts the number
of times of ejections executed by the heat generating elements 1e. In
addition, the dot counting means 25 independently counts four groups of
heat generating elements, and the printing duty calculating means 56
calculates a printing duty for each of the groups of heat generating
elements from the number of times of ejections executed for 10 seconds so
that preliminary ejection is performed corresponding to the calculated
printing duty.
For example, in the case that full area printing is continuously performed
for 10 seconds with 6.25 kHz, the number N.sub.max of printed dots is
represented by the following equation.
N.sub.max =(6.25.times.10.sup.3).times.10.times.16
=1.times.10.sup.6 (shots)
Thus, for example, in the case that a heat generating element group 1
performs ejection by 2.times.10.sup.5 (shots) for 10 seconds, a heat
generating element group 2 performs ejection by 1.times.10.sup.5 (shots)
for ten seconds, and a heat generating element group 3 performs ejection
by 1.times.10.sup.4 (shots) for ten seconds and a heat generating element
group 4 performs ejection by 7.times.10.sup.5 (shots) for ten seconds, the
printing duty (duty 1 to duty 4) to be borne by each heat generating
element group is expressed by the following equations.
duty 1.times.{(2.times.10.sup.5)/(1.times.10.sup.6)}.times.100
=20 (%)
duty 2={(3.times.10.sup.5)/(1.times.10.sup.6))}.times.100 =30 (%)
duty 3={(1.times.10.sup.4)/(1.times.10.sup.5)}.times.100 =1%
duty 4={(7.times.10.sup.5)/(1.times.10.sup.6)}.times.100 =70%
Preliminary ejection was performed for each of the heat generating element
groups in consideration of the foregoing results. One example representing
preliminary ejection conditions corresponding to the respective printing
duties is shown in Table 3 and Table 4.
TABLE 3
______________________________________
the number the number
the number
the number
of first of second of first of first
preliminary
preliminary
preliminary
preliminary
printing
ejection ejection ejection ejection
duty (%)
dots A dots B dots C dots
______________________________________
zero to
50 20 20 20
less than
10
10 or 100 40 40 40
more to
less than
20
20 or 150 50 50 50
more to
less than
30
30 or 200 70 70 70
more to
less than
40
40 or 250 90 90 90
more to
less than
50
50 or 300 100 100 100
more to
less than
60
60 or 350 120 120 120
more to
less than
70
70 or 400 140 140 140
more to
less than
80
80 or 450 150 150 150
more to
less than
90
90 or 500 170 170 170
more to
less than
100
______________________________________
TABLE 4
______________________________________
driving width of width of
frequency prepulse pause time main pulse
(Hz) (.mu.s) (.mu.s) (.mu.s)
______________________________________
first 6.25 .times. 1000
1.0 0.0 8.62
preliminary
ejection
second 500 1.0 0.0 4.2
preliminary
ejection A
third 500 1.0 0.9 4.2
preliminary
ejection B
fourth 500 1.0 1.8 4.2
preliminary
ejection C
______________________________________
FIG. 13 and FIG. 14 illustrates a series of steps of preliminary ejection
processings to be practiced in accordance with this embodiment. FIG. 13
shows a line feed interruption subroutine to be executed every time each
line is changed. FIG. 14 shows a 50 millisecond interruption subroutine to
be executed every 50 milliseconds. In this embodiment, the first
preliminary ejection and the second preliminary ejecting A to C as
mentioned above are performed during printing operation as well as every
10 seconds at the standby when the capping member 13 is parted away from
the ejection port plane 1a of the ink jet head 18, and moreover, they are
performed also after the wiping operation in the case that the number of
printed dots exceeds a predetermined one.
With the line feed interruption shown in FIG. 13, it is determined whether
or not preliminary ejection flag F.sub.1 and wiping flag F.sub.W are set
to 1, and in the case that it is found that the wiping flag F.sub.w is set
to 1, wiping operation is performed, and subsequently, first preliminary
ejection and second preliminary ejection A to C are practiced. After
completion of these processings, each flag is reset to 0, and moreover,
count value C.sub.T of the timer is reset to 0. In detail, it is
determined at Step S61 whether or not wiping flag F.sub.w is set to 1, and
in the case that it is determined it is set to 1, the subroutine goes to
Step S62 in which wiping operation is performed. Subsequently, in Step S
63, wiping flag F.sub.w is reset to 1, and moreover, in Step S64, timer
count value C.sub.T is reset to 0. Then, in Step 65, necessary data are
read from Table 3 and Table 4 and in Step S66 to Step 69, preliminary
ejections A to D are successively performed, and thereafter, in Step S70,
preliminary ejection flag F.sub.1 is reset to 0, and additionally, in Step
S71, total printed dot numbers N.sub.D1 to N.sub.D4 for the respective
heat generating element groups are rest to 0, whereby interrupt
processings are terminated.
On the other hand, in the case that it is determined in Step S61 that
wiping flag F.sub.W is not set to 1, the subroutine goes to Step S72 in
which it is determined whether or not preliminary ejection flag F.sub.1 is
st to 1. In the case that it is determined that preliminary ejection flag
F.sub.1 is set to 1, the subroutine goes to Step S65 and subsequent ones
but in the case that it is determined that the preliminarily ejection flag
F.sub.1 is reset to 0, interruption processings are terminated while
nothing is done.
On the other hand, with 50 millisecond interruption shown in FIG. 14, 10
second timer and printed dot number timer perform counting operation, and
in the case that the results derived from the counting operations exceed
prescribed values, preliminary ejection flag F.sub.1 and wiping flag
F.sub.w are set to 1. Namely, in Step S81, timer counted value C.sub.r is
raised up by one, and the subroutine goes to Step S82 in which it is
determined whether or not timer counted value C.sub.r exceeds 200. In the
case that it is determined that the timer counted value C.sub.4 exceeds
200, the subroutine goes to Step S83 in which preliminary ejection flag
F.sub.1 is set to 1, and in Step S84, printing duties 1 to 4 for
respective heat generating element groups are calculated. Thereafter, in
Step S85, respective heat generating element group printed dot numbers
N.sub.d1 to N.sub.d4 are read for 50 milliseconds till this time and Step
S86, respective heat generating element group printed dot numbers N.sub.D1
to N.sub.D4 till this time are calculated based on the following equations
.
N.sub.D1 =N.sub.D1 +N.sub.d1
N.sub.D2 =N.sub.D2 +N.sub.d2
N.sub.D3 =N.sub.D3 +N.sub.d3
N.sub.D4 =N.sub.D4 +N.sub.d4
Additionally, in Step 87, total printed dot number N.sub.D is calcualted
based on the following equations.
N.sub.D =N.sub.D1 +N.sub.D2 +N.sub.D3 +N.sub.D4
And, it is determined in Step 88 whether or not the total printed dot
number N.sub.D is larger than 1.5.times.10.sup.5. In the case that it is
determined that the total printed dot number N.sub.D is larger than
1.5.times.10.sup.5, the subroutine goes to Step S89 in which wining flag
F.sub.w is set to 1, and after printing duties 1 to 4 for the respective
heat generating element groups are calculated in Step S90, interruption
processings are terminated.
In the case that it is determined in Step S82 that the timer count value
C.sub.T l is 300 less, the subroutine goes to Step S85 and subsequent
ones, and in the case that it is determined in Step S88 that the total
printed dot number N.sub.D is 1.5.times.10.sup.5 or less, this
interruption processing is terminated.
The reason why sixteen heat generating elements 1e are divided into four
heat generating element groups like in this embodiment consists in that
since density fluctuation on an image with the heat generating element 1e
as a unit is hardly recognized, four heat generating elements 1e are
processed as an unit so as to reduce a load to be borne by a main body of
the ink jet apparatus. Therefore, in the case that calculation processing
means of the ink jet apparatus has some allowance, it is acceptable that a
quantity of deposition of the ink adhering ingredient I.sub.s is presumed
with respect to each heat generating element 1e among a plurality of heat
generating elements 1e. In this embodiment, printed dots are counted for
ten seconds to presume a quantity of deposition of the ink adhering
ingredient I.sub.s, and preliminary ejection is executed under the
conditions as described in Table 3 and Table 4, but it is preferable that
a quantity of deposition of the ink adhering ingredient I.sub.s is set to
an optimum value in association with the composition of ink or the
structure of ink jet apparatus.
In such a manner, when a quantity of deposition on the ink adhering
ingredient I.sub.s is on the heat generating element 1e is presumed every
heat generating element 1e group, and preliminary ejection is performed
corresponding to the quantity of deposition on the ink adhering ingredient
I.sub.s, adhering substance can be removed by cavitation induced at the
time defoaming, and it is possible to perform a printing operation with a
minimum quantity of ink ejection without any density fluctuation. In
addition, with respect to ink of which ejection quantity is quickly
reduced due to easy deposition on the surface of the heat generating
element 1e, according to the present invention, it is possible to remove
the ink adhering ingredient I.sub.s on the heat generating element 1e.
This means that the width of selecting of ink can be widened much more
than till this time.
With respect to a typical structure and operational principle of an ink jet
system, it is preferable to employ a fundamental principle as disclosed in
official gazettes of U.S. Pat Nos. 4,723,129 and 4,740,796. This type of
principle is applicable to either one of an on-demand type ink jet system
or a continuous type ink jet system. Especially, in the case of the
on-demand type ink jet system, a heat generating element disposed
corresponding to a sheet having ink held thereon or an ink passage is
caused to generate thermal energy by applying thereto at least one driving
signal for inducing rapid temperature rise in excess of appearance of a
phenomenon of a nucleate boiling. Moreover, a phenomenon of film boiling
appears on the heat functioning plane of an ink jet head. Consequently,
bubbles can be formed in ink while corresponding to the driving signal in
the one-to-one relationship. As bubbles grow or contract, ink is ejected
through the ejection opening to form at least one droplet. When this
driving signal is prepared in the form of a pulse, bubbles are immediately
adequately grown and contracted. Thus, ink ejection can be achieved with
excellent responsiveness. With respect to the pulse-shaped driving signal,
it is recommendable that reference is made to official gazettes of U.S.
Pat. Nos. 4,463,359 and 4,345,262. When the conditions described in an
official gazette of U.S. Pat. No. 4,313,124 associated with the rate of
temperature raise of the thermal working surface are employed, printing
operation can be achieved with more excellent results.
With respect to the structure of an ink jet head, in addition to a
combination structure made among ejection port, ink passage and heat
generating element (straight liquid passage or passage at a right angle
relative to the foregoing one), the structure disclosed in official
gazettes of U.S. Pat. Nos. 4,558,333 and 4,459,600 associated with the
thermal functioning portion and bent region are incorporated in the
present invention. Further, the structure based on an official gazette of
Japanese Patent Application Laid-Open NO. 123670/1984 disclosing the
structure for allowing a common slit to serve as an ejecting potion of a
heat generating element relative to a plurality of heat generating
elements and the structure based on an official gazette of Japanese Patent
Application Laid-Open NO. 138461/1984 disclosing the structure including
an opening hole for absorbing the pressure wave of thermal energy
corresponding an ejection portion are effectively employable for the
present invention. Namely, regardless of the contour of the ink jet head,
according to the present invention, printing can reliably be achieved at a
high efficiency.
In addition, the present invention can advantageously be applied to a full
line type ink jet head having a length corresponding to a maximum width
which can be printed by the ink jet apparatus. As such an ink jet head as
mentioned above, either of the structure satisfying a length by
combination of a plurality of ink jet head and the structure as a single
integrally formed ink jet head is acceptable.
Further, among the serial type ink jet heads, an ink jet head fixed to the
main body of the apparatus or an exchangeable tip type ink jet head which
makes it possible to be electrically connected by fitting to the main body
of the apparatus and to which ink can be supplied or a cartridge type ink
jet head including an ink tank integrated with the ink jet head itself are
effectively employable for the present invention.
As the structure of the ink jet apparatus of the present invention, since
additional arrangement of ejection recovering means of the ink jet head,
and preparative assisting means can stabilize effects of the present
invention, they are preferably employable for the present invention.
Concretely, they are exemplified by capping means fitted to ink jet head,
cleaning means, pressurizing means or sucking means, heat generating
element and heating element separately arranged from the heat generating
element, preparative heating means for performing heating by using a
combination of the aforementioned elements, and preparative ejecting means
adapted to perform ejecting separately from printing.
With respect to the kind of the number of ink jet heads to be mounted on
the ink jet apparatus, a single ink jet head is arranged for, e.g., a
monochromatic color. Alternatively, plural ink jet heads may be arranged
corresponding to plural kind of inks each different printing color and
density. For example, as a printing mode of the ink jet apparatus, not
only a printing mode having a main color such as black color employed but
also plural printing modes based on different colors or full color derived
from mixing of colors are effectively employable for the present
invention. In this case, the ink jet head may integrally be constructed or
plural sets of ink jet heads may be combined with each other.
In the embodiment as mentioned above, each ink to be used has been
explained as a liquid. Alternatively, ink which is kept solid at a
temperature equal to or lower than a room temperature but softened or
liquidized at the room temperature may be used. In the ink jet system,
since the temperature of ink to be used is generally controllably adjusted
within the temperature range of 30 .degree. C. or more to 70.degree. C. or
less so as to allow the viscosity of the ink to be maintained within the
stable range, ink which is liquidized when a recording signal is applied
to the printing head may be used. To positively prevent the temperature of
ink from being elevated due to the thermal energy applied to the recording
head by utilizing the energy arising when the solid state of ink is
transformed into the liquid state or to prevent the ink from being
vaporized, ink which is kept solid in the unused state by liquidized on
receipt of heat may be used. At any rate, the present invention can be
applied to the case that in response to a recording signal, ink is
liquidized on receipt of thermal energy and the liquid ink is then ejected
from the recording head, the case that ink starts to be solidified when an
ink droplet reaches a printing medium, and the case that ink having such a
nature that it is liquidized only in response to application of thermal
energy to the printing head is used.
According to the present invention, a most effective ink jet system
applicable to the inks as mentioned above is a film boiling system.
In addition, the ink jet apparatus of the present invention can be employed
not only as image output terminal of an information processing unit such
as a computer or the like but also as an output unit of a copying machine
combined with an optical reader as an output unit of a facsimile having a
signal sending/receiving function.
According to the present invention, since ink adhering ingredient deposited
on a heat generating element while coming in contact with ink owing to
defoaming position changing means can be removed within a wide range,
density fluctuation in character, image or the like can be removed
compared with the conventional ink jet apparatus.
Since ink adhering ingredient deposited on the printing element can
effectively removed by preliminary ejection conduced with the aid of ink
adhering ingredient depositing means and ink adhering ingredient peeling
means, the kind of ink ingredient utilizable by the ink jet system can be
augmented.
Moreover, a quantity of consumption of ink necessary for preliminary
ejection can be minimized by carrying out preliminary ejection
corresponding to the state of usage of the heat generating element.
The present invention has been described in detail with respect to
preferred embodiments, and it will be now be that changes and
modifications may be made without departing from the invention in its
broader aspects, and it is the intention, therefore, in the appended
claims to cover all such changes and modifications as fall within the true
spirit of the invention.
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